# Program to decrypt using Caesar cipher
# ECS 10, Winter 2012
# Matt Bishop, Mar. 7, 2012
import string

#
# this corresponds to a key of 'D' ('A' = 0, ... 'Z' = 25)
#
key = 3
#
# ask user for input message (plaintext)
#
cipher = input("Enter your message here: ")
#
# initialize output (plaintext)
#
plain = ""
#
# decipher each character and append it to current plaintext
#
for i in cipher:
        # leave non-letters alone
        if i in "ABCDEFGHIJKLMNOPQRSTUVWXYZ":
                # map the letter into 0 . . 25
                n = ord(i) - ord('A')
                # shift it
                n = (n - key) % 26
                # map it back into a letter
                lett = chr(ord('A') + n)
        elif i in "abcdefghijklmnopqrstuvwxyz":
                # map the letter into 0 . . 25
                n = ord(i) - ord('a')
                # shift it
                n = (n - key) % 26
                # map it back into a letter
                lett = chr(ord('a') + n)
        else:
                lett = i
        # now append it
        plain = plain + lett
#
# print it, surrounded by quotes
#
print("\"%s\"" % plain)